How long would Japan hold out?

How long would the Imperial Japanese Navy and Japan remain in the war?

Japan would probably pass through 1939 without a decisive fleet attack, but the complete war could last roughly three or four years before blockade and economic exhaustion forced surrender.

Allied mobilization, force concentration, and blockade construction would probably dominate 1939 rather than an immediate assault on Japan. That delay lets the Japanese fleet remain intact for a time, but it also lets a broad coalition expand faster than Japan can replace fuel, ships, aircraft, and crews. The likely end is neither an atomic campaign nor an early invasion of the home islands. Several years of maritime pressure instead grind down the economy and create the conditions in which Japan's political leadership must decide whether to continue.